Import large model file into Blender
Method 1:

The Blender documentation says:


  Use ABC if you want to import/export a large amount of scene data.


So the idea is to find a way to convert your big model from PLY to Alembic. Sadly, I didn't find any converters that generate alembic, but in their GitHub repository, there is an example called WFObjConvert. I'm not used to C++ and don't know about the conversion direction, but the line

OBJ::ParseOBJ( reader, argv[1] );


from the test files indicates that it is taking OBJ and converting to ABC.

If you get this to work, you need to convert your model to Wavefront first. That should be a lot easier due to the popularity of the format. This site should to the job for you.

Method 2:

Just use the converter and convert your file into several other formats Blender can import and try them out.

Edit:

Using an online converter isn't that a good idea with this file size. Use some offline converter like that one instead.